Folk healers used medicinal plants to treat diseases for ages. Due to the development of modern medicine, the local wisdom of folk healers is declining regarding the use of medicinal plants in treating diseases. Therefore, ancestral knowledge has to be systematically documented. This study was performed using a mixed-method study, which comprised the following: a qualitative approach through a face-to-face open-ended interview using a semistructured questionnaire; identification and classification of medicinal plants used by different ethnic group folk healers in Buriram Province, Thailand. For the interview, all participants were male folk healers aged over 50 years. All healers believed that the human body is made up of four elements: earth, water, wind, and fire. Illness or disease results from an imbalance of the four elements. The results showed that folk healers used 220 medicinal plants from 76 families for therapeutic purposes. The top three families were Fabaceae, Euphorbiaceae, and Poaceae, respectively. Moreover, the most commonly used parts were root (26.1%), aerial stem (23.5%), and tuber/bulb (13.2%). Most herbal remedies were administered orally (84.62%). The top three most important plants with a use value index of 0.64 were Walsura villosa, Piper nigrum, and Smilax glabra. The most treated diseases and symptoms were gastrointestinal disorders (16.07%), cancer (10.71%), and respiratory conditions (9.82%). In conclusion, the uses of medicinal plants and practice patterns of folk healers were systematically documented. Verification of bioactive compounds, chemical profiling in vitro and in vivo, and/or clinical studies of the medicinal plants are required to confirm the efficacy.